Those of you working with Arduino and Ethernet projects may only have one running at a time, so the MAC address used is most likely a default or something witty like DE:AD:BE:EF:FE:ED. However as soon as you run more than one the conflicting MAC addresses require altering within the Arduino sketch which can be quite inconvenient if you're working with many units. To solve this problem the people from one of our resellers - nicegear in New Zealand have released a simple but logical solution for this problem with their MAC protoshield:

it's a nifty little shield that contains an I2C-controlled EEPROM each with a unique MAC address. By inserting their code into your device's sketch it can now retrieve the unique MAC from the shield (and use the spare 2Kbit on the EEPROM) saving individual sketch uploads for each device. The shield also has clearance for the RJ45 socket and our PoE regulator if using our Freetronics EtherTen board. So for more information on the shield visit the nicegear website. And for more, we're on twitter and Google+, so follow us for news and product updates as well.

When putting together your next Internet-enabled Arduino project - save time, space and money with the Freetronics EtherTen. Apart from being fully Arduino Uno-compatible, it has onboard Ethernet, microSD socket, full USB interface (so you don't need a costly FTDI cable just to upload a sketch!) and supports optional Power-over-Ethernet.